Characteristics of thunder pertinent to tropical lightning

Acoustic effects of lightning flashes are not well studied. Thunder also destructive as electric fields do. Thunder flashes of tropical lightning occurred in Hambantota (81
⁰
0'E, 6
⁰
10'N) close to the southern coast of Sri Lanka were studied. About 90 thunder flashes recorded with the sampling rate of 100 kS/s in 45 s windows were analyzed to identify their characteristics and damaging effects. Results of the analysis on duration of thunder flashes, peak sound pressure levels, occurrence of thunder claps and frequency distribution were presented. The shortest and longest duration of thunder recorded were 2.2 sec and 33.7 sec respectively. About 75% of thunder flashes were remained for about 5-20 sec. The frequency spectrum of a thunder signal could spread up to 1500 Hz. The peak sound pressure level of 30% of recorded thunder flashes at least 3 km away from the lightning were higher than 2 Nm
^-2
(100 dB). One to five claps were identified in thunder flashes with 62% having 1 or 2 claps. Sound pressure level, frequency range and its duration are required quantities to estimate the harmful effects of thunder.